Mechanical couplings for joining plain end pipe elements together end-to-end comprise interconnectable segments that are positionable circumferentially surrounding the end portions of co-axially aligned pipe elements. The term “pipe element” is used herein to describe any pipe-like item or component having a pipe-like form. Pipe elements include pipe stock, pipe fittings such as elbows, caps and tees as well as fluid control components such as valves, reducers, strainers, restrictors, pressure regulators and the like.
Each mechanical coupling segment comprises a housing having projections which extend inwardly from the housing. Toothed retainers may be used to form the projections for couplings for plain end pipe elements. When the retainers are properly oriented in the segments, engagement between the teeth and the pipe elements provides mechanical restraint to the joint and ensures that the pipe elements remain coupled even under high internal pressure and/or external forces. The housings also define an annular channel or pocket that receives a ring gasket or seal, typically an elastomeric ring which engages the ends of each pipe element and cooperates with the segments and the pipe elements to provide a fluid tight seal. The segments have connection members, typically in the form of lugs which project outwardly from the housings. The lugs are adapted to receive fasteners, such as nuts and bolts, which are adjustably tightenable to draw the segments toward one another.
Some retainers use teeth that are angularly oriented with respect to a line extending radially from an axis coaxial with the central space. The proper angular orientation allows the teeth to be “self-actuating”, i.e., the mechanical engagement between the teeth and the pipe elements increases with increasing force on the pipe elements trying to draw or push them out of the coupling. Hence, the force resisting withdrawal increases with the applied force that would otherwise cause withdrawal. However, if such retainers are oriented improperly, for example, if the retainer is reversed within the coupling, then the teeth will not be self-actuating against forces which would draw or push the pipe element out of the coupling. Thus the retainer would not provide sufficient mechanical engagement against withdrawal and the pipe elements will not be securely held within the coupling. For couplings having retainers it is difficult to determine if the retainers are properly oriented once the coupling has been installed. It would be advantageous if pipe couplings could be designed so that the user is alerted if the retainer is not properly oriented during assembly of the joint.